JP7728360B2 - Electric brake device and drive unit - Google Patents

Description

The present invention relates to an electric brake device and a drive unit.

Patent document 1 discloses an electric brake device that includes a spindle driven by an electric motor and a mechanical reservoir (power spring) that stores energy through torsion. The mechanical reservoir has a first end that engages with the spindle and a second end that engages with a bracing element. The mechanical reservoir absorbs energy while the spindle rotates, and this energy causes the spindle to rotate in the reverse direction when no current is applied to the electric motor, releasing the brake.

US Patent Application Publication No. 2013/0264153

However, in the device described in Patent Document 1, the bracing element, which engages with one end of the spiral spring and operates by sliding when torque exceeds a predetermined value, thereby suppressing excessive energy accumulation, is located at the end of the spindle in the direction of the rotation axis, which could reduce the layout flexibility of the electric brake device.

One of the objects of the present invention is to provide an electric brake device and drive unit that can suppress a reduction in layout flexibility.

As a means for solving the above problem, the electric brake device of the present invention is characterized by comprising: an electric motor; a rotating member that rotates when driven by the electric motor; a linear-acting member that moves linearly in the axial direction of the disk as the rotating member rotates, thereby moving a friction pad; a torque transmission member; a torque limiter mechanism that is arranged between the rotating member and the torque transmission member and that applies a rotational resistance force between the rotating member and a torque limiter mechanism as the rotating member rotates, and causes the torque transmission member to rotate together with the rotating member until the rotational resistance force exceeds a predetermined value; a fixed part; and an elastic member that has one end connected to the torque transmission member and the other end connected to the fixed part, and that stores elastic energy as the torque transmission member rotates relative to the fixed part as the rotating member rotates.

The electric brake device according to the present invention is characterized in that it comprises an electric motor, a rotating member connected to the electric motor, a linear-acting member threadedly engaged with the rotating member, a torque transmission member, the torque limiter mechanism that is disposed between the rotating member and the torque transmission member and applies a rotational resistance force between the rotating member and the torque limiter mechanism as the rotating member rotates, causing the torque transmission member to rotate together with the rotating member until the rotational resistance force exceeds a predetermined value, a fixed part, and a torsion spring having one end connected to the torque transmission member and the other end connected to the fixed part.

Furthermore, a drive unit according to the present invention is a drive unit that provides power to press a friction pad against a disc of a disc brake, and is characterized in that it comprises: an electric motor; a rotating member that rotates when driven by the electric motor; a linear-moving member that moves linearly as the rotating member rotates; a torque transmission member; a torque limiter mechanism that is disposed between the rotating member and the torque transmission member and that applies a rotational resistance force between the rotating member and the torque limiter mechanism as the rotating member rotates, and causes the torque transmission member to rotate together with the rotating member until the rotational resistance force exceeds a predetermined value; a fixed portion; and an elastic member that has one end connected to the torque transmission member and the other end connected to the fixed portion and that stores elastic energy as the torque transmission member rotates relative to the fixed portion as the rotating member rotates.

According to one embodiment of the present invention, it is possible to suppress a decrease in layout flexibility.

1 is a cross-sectional view of a main portion of a disc brake according to a first embodiment. FIG. 2 is an exploded perspective view of a rotary-to-linear motion conversion mechanism and a fail-open mechanism, including a piston, employed in the disc brake according to the first embodiment. FIG. 2 is an exploded perspective view of a fail-open mechanism employed in the disc brake according to the first embodiment. FIG. 2 is a plan view of the disc brake according to the first embodiment, showing a state in which a spring clutch is attached to a spindle and before a torque transmission member is assembled. FIG. 2 is a plan view of the disc brake according to the first embodiment, showing a state in which a spring clutch is attached to a spindle and a torque transmission member is assembled. 1 is a cross-sectional view of a disc brake according to a first embodiment, showing a state in which a retaining ring and a spring clutch are mounted between a spindle and a torque transmission member. FIG. 5A and 5B are cross-sectional views of the disc brake according to the first embodiment, showing the operation of the spring clutch in stages. 5A to 5C are schematic diagrams showing the operation of the fail-open mechanism of the disc brake according to the first embodiment in stages. FIG. 11 is an exploded perspective view of a rotary-to-linear motion conversion mechanism and a fail-open mechanism, including a piston, employed in a disc brake according to a second embodiment. FIG. 10 is a cross-sectional view showing a truncated cone spring provided between the spindle and the torque transmission member of the disc brake according to the second embodiment. FIG. 11 is a schematic diagram of a main part of a disc brake according to a third embodiment.

The present embodiment will be described in detail below with reference to FIGS.
The disc brakes 1A, 1B, and 1C according to the first to third embodiments of the present invention are electric brake devices that, during normal driving, generate braking force by driving an electric motor 32. In the following description, the inside of the vehicle (inner side) will be referred to as one end side (cover member 30 side), and the outside of the vehicle (outer side) will be referred to as the other end side (disc rotor D side), as appropriate.

First, a disc brake 1A according to a first embodiment will be described with reference to FIGS.
Referring to Fig. 1, a disc brake 1A according to the first embodiment includes a pair of inner and outer brake pads 2 and 3 arranged on either side of a disc rotor D attached to a rotating part of a vehicle in the axial direction, and a caliper 4. The disc brake 1A is configured as a floating caliper. The pair of inner and outer brake pads 2 and 3, and the caliper 4 are supported by a carrier 5 fixed to a non-rotating part of the vehicle, such as a knuckle, so as to be movable in the axial direction of the disc rotor D. The inner and outer brake pads 2 and 3 correspond to friction pads. The disc rotor D corresponds to a disc.

Referring to Figure 1, the caliper 4 comprises a caliper body 8, which is the main body of the caliper 4, and a drive unit 9 that provides power to press the inner brake pad 2 and outer brake pad 3 against the disc rotor D. The caliper body 8 is arranged at the base end facing the inner brake pad 2 and comprises a cylindrical cylinder portion 13 that opens facing the inner brake pad 2, and a pair of claw portions 14, 14 that extend from the cylinder portion 13 across the disc rotor D to the outer side and are arranged at the tip side (other end) facing the outer brake pad 3. Note that Figure 1 shows only one of the pair of claw portions 14, 14.

1 and 2, a piston 18 is accommodated in the cylinder portion 13 of the caliper body 8, i.e., in the cylinder bore 16 of the cylinder portion 13, so as to be non-rotatable relative to the cylinder portion 13 and movable axially. The piston 18 presses against the inner brake pad 2 and is formed in a cup shape with a bottom. The piston 18 is accommodated in the cylinder bore 16 so that its bottom faces the inner brake pad 2. The piston 18 is supported non-rotatable relative to the cylinder bore 16 of the cylinder portion 13, and ultimately the caliper body 8, by anti-rotation engagement, such as concave-convex engagement, between the bottom and the inner brake pad 2. Referring to FIGS. 2 and 3, a plurality of vertical engagement grooves 19 extending axially are formed circumferentially on the inner peripheral surface of the piston 18. In this embodiment, the vertical engagement grooves 19 are formed at two locations spaced 180° apart.

Referring to Figure 1, a seal member 20 is disposed on the inner circumferential surface at the other end of the cylinder bore 16 of the cylinder portion 13. The piston 18 is housed in the cylinder bore 16 and is able to move axially while in contact with this seal member 20. A dust boot 21 is interposed between the outer wall portion on the bottom side of the piston 18 and the inner circumferential surface at the other end of the large-diameter cylinder bore 16. The seal member 20 and dust boot 21 prevent foreign matter from entering the cylinder bore 16 of the cylinder portion 13.

A gear housing 28 is integrally connected to the bottom wall 23 side (one end side) of the cylinder portion 13. An insertion hole 25 is provided in the bottom wall 23 of the cylinder portion 13, and a spindle 40 (described later) extends into the gear housing 28 through the insertion hole 25. The opening on one end side of the gear housing 28 is airtightly closed by a cover member 30. A drive unit 9 is disposed in the gear housing 28 and the cylinder bore 16 of the cylinder portion 13. The drive unit 9 transmits rotation from an electric motor 32 to a piston 18 housed in the cylinder bore 16 of the cylinder portion 13, and uses the thrust of the piston 18 to press the inner brake pad 2 and outer brake pad 3 against the disc rotor D.

Referring to Figure 1, the drive unit 9 includes an electric motor 32, a reduction gear mechanism 33 to which rotation from the electric motor 32 is transmitted and which amplifies the rotational torque from the electric motor 32, a rotary-to-linear motion conversion mechanism 34 that converts the rotation from the reduction gear mechanism 33 into linear motion and applies thrust to the piston 18, and a fail-open mechanism 35 that releases the braking force when the electric motor 32 cannot operate normally due to a power supply failure or the like during braking. The drive of the electric motor 32 is controlled by commands from a control device (not shown).

During braking during normal driving, the control device controls the rotation (rotation direction, rotation speed, etc.) of the electric motor 32 based on various detection signals, such as detection signals from detection sensors (not shown) that respond to driver requests and detection sensors (not shown) that detect various situations in which braking is necessary, detection signals from wheel speed detection sensors (not shown) that detect wheel speed, detection signals from rotation angle detection means (not shown) that detects the rotation angle of the electric motor 32, and detection signals from thrust sensors (not shown) that detect thrust (pressing force) from the inner and outer brake pads 2, 3 to the disc rotor D.

The electric motor 32 and reduction gear mechanism 33 are housed within the gear housing 28. The reduction gear mechanism 33 amplifies the rotational torque from the electric motor 32 and transmits it to the rotary-to-linear motion conversion mechanism 34. A planetary gear mechanism or the like is used for the reduction gear mechanism 33. The rotary-to-linear motion conversion mechanism 34 and the fail-open mechanism 35 are housed within the cylinder bore 16 of the cylinder section 13. The rotary-to-linear motion conversion mechanism 34 includes a spindle 40 to which rotation from the reduction gear mechanism 33 is transmitted, and a nut member 41 that threads onto the spindle 40.

In the disc brake 1A according to the first embodiment, the spindle 40 corresponds to the rotating member, and the nut member 41 corresponds to the linear member. Referring to Figures 1 and 2, the spindle 40 is provided with a splined shaft portion 43 provided at one end thereof, a male threaded portion 44 provided at the other end thereof, an annular support portion 45 protruding radially from the outer circumferential surface of the male threaded portion 44 at the one end thereof, and a cylindrical support portion 46 provided between the annular support portion 45 and the male threaded portion 44.

1 and 2, the spline shaft portion 43 of the spindle 40 is connected to the output member (not shown) of the reduction gear mechanism 33 inside the gear housing 28 so as to be non-rotatable relative to the output member. As a result, rotational torque can be transmitted between the output member of the reduction gear mechanism 33 and the spindle 40. Referring to FIG. 1, a thrust bearing 50 is disposed between the annular support portion 45 of the spindle 40 and the bottom wall 23 of the cylinder portion 13. The thrust bearing 50 rotatably supports the spindle 40 on the bottom wall 23 of the cylinder portion 13. The thrust bearing 50 comprises a cylindrical thrust member 51 disposed on the bottom wall 23 side of the cylinder portion 13, and a plurality of thrust balls 52 disposed to roll between the thrust member 51 and the annular support portion 45 of the spindle 40.

The other end surface of the thrust member 51 is formed with a rolling groove 54 along which each thrust ball 52 rolls. One end surface of the annular support portion 45 of the spindle 40 is formed with a rolling groove 55 along which each thrust ball 52 rolls. A plurality of thrust balls 52 are freely disposed between the rolling groove 54 of the thrust member 51 and the rolling groove 55 provided in the annular support portion 45 of the spindle 40. These thrust balls 52 are held at regular intervals in the circumferential direction by a retainer 57. The spindle 40 is inserted into the thrust member 51 of the thrust bearing 50. Referring to Figures 1 and 2, a notched step 60 is formed at one end of the annular support portion 45 of the spindle 40, with the outer periphery thereof cut out in both the radial and axial directions. A retaining ring 98 is disposed in this notched step 60.

Referring to Figures 1 and 2, the spindle 40 has a cylindrical support portion 46 between the annular support portion 45 and the male thread portion 44. The outer diameter of the cylindrical support portion 46 is larger than the outer diameter of the male thread portion 44 and smaller than the annular support portion 45. The outer diameter of the cylindrical support portion 46 is approximately the same diameter as the outer peripheral surface of the fixing member 70, which will be described later. An annular groove portion 48 is formed in the outer peripheral surface of the cylindrical support portion 46. A spring clutch 73, which will be described later, is disposed in this annular groove portion 48.

Referring to Figures 1 and 2, the nut member 41 is disposed radially outward of the male threaded portion 44 of the spindle 40. The nut member 41 is formed in a cylindrical shape that is long along the axial direction. A female threaded portion 62 is formed on the inner peripheral surface at one end of the nut member 41. The male threaded portion 44 of the spindle 40 and the female threaded portion 62 of the nut member 41 are threadedly engaged with each other. The nut member 41 is supported so as not to rotate relative to the piston 18, and therefore the cylinder portion 13. This allows the nut member 41 to move freely along the axial direction as the spindle 40 rotates.

Referring to Figure 1, a fail-open mechanism 35 is provided within the cylinder bore 16, radially outward of the nut member 41, which can quickly release the braking force in the event of a power failure or other problem. Also referring to Figures 2 and 3, the fail-open mechanism 35 includes a fixed member 70, a torque transmission member 71, a torsion spring 72, and a spring clutch 73. The fixed member 70 is formed cylindrically as a whole. The nut member 41 is inserted into the fixed member 70.

1 to 3, the other end of the fixing member 70 is provided with an annular protrusion 76 that protrudes radially outward. A spring accommodating recess 78 is formed on the outer peripheral surface of the annular protrusion 76 at a predetermined circumferential position. The other end of the torsion spring 72 is accommodated in the spring accommodating recess 78. An engaging protrusion 80 that protrudes radially outward is formed on the outer peripheral surface of the annular protrusion 76. In this embodiment, the engaging protrusions 80 are formed in two locations at 180° intervals to correspond to the vertical engaging grooves 19 formed in the piston 18. When the fixing member 70 is inserted into the piston 18, the engaging protrusions 80 of the fixing member 70 engage with the vertical engaging grooves 19 formed in the piston 18. As a result, the fixing member 70 is supported so as not to rotate relative to the piston 18 and, ultimately, the cylinder portion 13. In the disc brake 1A according to the first embodiment, the fixing member 70 corresponds to the fixing portion.

1, the torque transmission member 71 is disposed so as to radially cover the annular protrusion 76 of the fixing member 70 from one end side and the annular support portion 45 of the spindle 40. Also referring to FIGS. 2 and 3, the torque transmission member 71 is formed cylindrically as a whole. The torque transmission member 71 comprises a small-diameter cylindrical portion 84, which is its main body, and a large-diameter cylindrical portion 85 that is continuous from one end of the small-diameter cylindrical portion 84 to the other end side. The small-diameter cylindrical portion 84 extends from the annular protrusion 76 of the fixing member 70 toward the one end side, covering the entire axial length of the columnar support portion 46 of the spindle 40. As a result, the fixing member 70 and the small-diameter cylindrical portion 84 of the torque transmission member 71 are disposed so as to overlap each other when viewed radially. The large-diameter cylindrical portion 85 radially covers the annular support portion 45 of the spindle 40 and protrudes slightly toward the one end from one end face of the annular support portion 45. As a result, the annular support portion 45 of the spindle 40 and the large-diameter cylindrical portion 85 of the torque transmission member 71 are arranged to overlap each other when viewed from the radial direction. The torque transmission member 71 is supported rotatably around the fixed member 70 and the annular support portion 45 of the spindle 40.

2 and 3, a radially penetrating spring accommodating notch 88 is formed in the peripheral wall of the large-diameter cylindrical portion 85 at a predetermined circumferential position. The spring accommodating notch 88 is formed across the entire axial length of the large-diameter cylindrical portion 85. One end of the torsion spring 72 is accommodated in the spring accommodating notch 88. With reference to FIGS. 1 and 4 to 6, a radially penetrating engagement slit 90 is formed at a predetermined circumferential position at the boundary between the large-diameter cylindrical portion 85 and the small-diameter cylindrical portion 84. The engagement slit 90 extends slightly axially toward the small-diameter cylindrical portion 84. A tip end 92 of the spring clutch 73, described below, engages with this engagement slit 90. In the disc brake 1A according to the first embodiment, this engagement slit 90 corresponds to the fitting portion.

Referring to FIG. 1, the torsion spring 72 is arranged along the outer peripheral surface of the small-diameter cylindrical portion 84 of the torque transmission member 71. In other words, the small-diameter cylindrical portion 84 of the torque transmission member 71 and the torsion spring 72 are arranged so as to overlap each other when viewed radially. In the disc brake 1A according to the first embodiment, the torsion spring 72 corresponds to the elastic member. Referring to FIGS. 2 and 3, one end of the torsion spring 72 is bent so as to extend in the axial direction. The other end of the torsion spring 72 is also bent so as to extend in the axial direction. Note that, referring to FIGS. 2 and 3, both ends of the torsion spring 72 are provided at different positions along the circumferential direction. For example, in the disc brake 1A according to the first embodiment, the axial ends of the torsion spring 72 are provided at different positions by approximately 45° along the circumferential direction.

As described above, the torsion spring 72 is arranged along the outer peripheral surface of the small-diameter cylindrical portion 84 of the torque transmission member 71. Referring to Figures 2 and 3, one end of the torsion spring 72 is accommodated in a spring accommodating notch 88 provided in the large-diameter cylindrical portion 85 of the torque transmission member 71. Meanwhile, the other end of the torsion spring 72 is accommodated in a spring accommodating recess 78 provided in the annular protrusion 76 of the fixed member 70. In this way, the fixed member 70 and the torque transmission member 71 are connected via the torsion spring 72.

1 and 4 to 6, a spring clutch 73 is disposed between the annular groove 48 provided on the outer peripheral surface of the cylindrical support portion 46 of the spindle 40 and the small-diameter cylindrical portion 84 of the torque transmission member 71. In the disc brake 1A according to the first embodiment, the spring clutch 73 corresponds to the torque limiter mechanism. The spring clutch 73 functions as a one-way torque limiter that applies rotational resistance only to rotation of the spindle 40 in one direction (in this embodiment, rotation in the braking direction). Also referring to FIG. 2, the spring clutch 73 is configured by a rod-shaped body with a circular cross section that is curved into a C-shape in a plan view. The spring clutch 73 is configured from a tip portion 92 extending radially outward and a coil portion 93 that is wound in a single arc shape and continues from the tip portion 92.

Referring to Figures 4 to 6, the coil portion 93 of the spring clutch 73 is wound around the annular groove 48 provided on the outer peripheral surface of the cylindrical support portion 46 of the spindle 40. The tip portion 92 of the spring clutch 73 engages with an engagement slit portion 90 provided in the torque transmission member 71. Referring to Figure 1, the spring clutch 73 and torsion spring 72 are arranged so as to overlap each other when viewed from the radial direction. The spring clutch 73 is configured to provide rotational resistance to rotation in the rotational direction when the spindle 40 is braked, while allowing rotation in the rotational direction when the spindle 40 is released from the brake.

Referring to Figures 4 to 7, during assembly, the coil portion 93 of the spring clutch 73 is wound around the annular groove 48 provided on the outer peripheral surface of the cylindrical support portion 46 of the spindle 40 with a predetermined tightening force (predetermined set load) (see the black arrow in Figure 7(a)). Furthermore, the maximum rotational resistance force exerted by the spring clutch 73 when the spindle 40 rotates in the braking direction (the maximum tightening force from the spring clutch 73 toward the radial center of the cylindrical support portion 46 of the spindle 40) is set to be approximately the same as the spring force when the torsion spring 72 is elastically deformed a predetermined amount in the torsional direction. In other words, when the spindle 40 rotates in the braking direction, the rotation of the spindle 40 is transmitted to the torque transmission member 71 via the spring clutch 73 until the rotational resistance force (the clamping force from the spring clutch 73 toward the radial center of the cylindrical support portion 46 of the spindle 40) between the annular groove portion 48 of the cylindrical support portion 46 of the spindle 40 and the coil portion 93 of the spring clutch 73 exceeds a predetermined elastic deformation amount (predetermined spring force) in the torsional direction of the torsion spring 72.

1, 2, and 6, an annular groove 95 is formed on the inner circumferential surface of the large-diameter cylindrical portion 85 of the torque transmission member 71. A retaining ring 98 is formed between the notched step 60 provided at one end of the annular support portion 45 of the spindle 40 and the annular groove 95 provided on the inner circumferential surface of the large-diameter cylindrical portion 85 of the torque transmission member 71. As a result, axial movement of the spindle 40 relative to the torque transmission member 71 is restricted. Thus, referring to FIG. 1, within the cylinder bore 16 of the cylinder portion 13, the spindle 40, the nut member 41, the fixing member 70, the torque transmission member 71, the torsion spring 72, and the piston 18 are arranged in this order from the inner radial direction to the outer radial direction. In other words, the spindle 40, the nut member 41, the fixing member 70, the torque transmission member 71, the torsion spring 72, and the piston 18 are arranged so as to overlap one another when viewed radially.

Next, the braking and braking release actions during normal driving in the disc brake 1A according to the first embodiment will be described based on FIGS. 7 and 8, and also with reference to FIG. 1 as needed.
When braking during normal driving, the drive unit 9 is activated by a command from the control device. Specifically, the electric motor 32 is driven, and its rotation in the braking direction is transmitted to the spindle 40 via the reduction gear mechanism 33. When the spindle 40 subsequently rotates in conjunction with the rotation of the reduction gear mechanism 33, the nut member 41 threadedly engaged with the spindle 40 advances, moving the piston 18 forward as shown in FIG. 8( b ) from the state shown in FIG. 8( a ). The advance of the piston 18 presses the inner brake pad 2 against the disc rotor D.

Then, due to the reaction force against the pressing force of the piston 18 on the inner brake pad 2, the caliper body 8 moves inward relative to the carrier 5, and the claws 14, 14 press the outer brake pad 3 against the disc rotor D. As a result, the disc rotor D is clamped between the pair of inner and outer brake pads 2, 3, generating a frictional force, which in turn generates a braking force for the vehicle.

During this braking, referring to Figures 7(b) and 8(a), the spindle 40 rotates in the braking direction (see the open arrow in Figure 7(b) and the filled arrow in Figure 8(a)), and as shown in Figure 7(b) from the state in Figure 7(a), the tip end 92 of the spring clutch 73 abuts against one of the opposing wall surfaces 90A that faces along the circumferential direction of the engagement slit portion 90 of the torque transmission member 71, and the clamping force by the spring clutch 73 toward the radial center of the spindle 40 (the rotational resistance force between the annular groove portion 48 of the cylindrical support portion 46 of the spindle 40 and the spring clutch 73) gradually increases (see the filled arrow in Figure 7(b)).As a result, referring to Figure 8, as the spindle 40 rotates, the torque transmission member 71 rotates in the braking direction via the spring clutch 73. Then, when the torque transmission member 71 rotates in the braking direction relative to the fixed member 70, which is supported non-rotatably, the torsion spring 72 arranged between the torque transmission member 71 and the fixed member 70 is elastically deformed in the torsional direction, and elastic energy is stored.

Continuing with reference to Figure 8(b), when the spindle 40 rotates in the braking direction and the spring force (restoring force) accumulated in the torsion spring 72 reaches a certain amount, i.e., when the torsion spring 72 reaches a predetermined amount of elastic deformation along the torsional direction, the spring force exceeds the rotational resistance force generated between the annular groove 48 of the spindle 40 and the spring clutch 73, causing slippage between the annular groove 48 of the spindle 40 and the spring clutch 73. As a result, the torque transmission member 71 does not rotate in the braking direction, and the spring force accumulated in the torsion spring 72 is limited to a certain amount.

If the spring force stored in the torsion spring 72 subsequently decreases even slightly, the rotational resistance generated between the annular groove 48 of the spindle 40 and the spring clutch 73 again exceeds the spring force of the torsion spring 72, and the rotation of the spindle 40 is once again transmitted to the torque transmission member 71 via the spring clutch 73. The torsion spring 72 then elastically deforms in the torsional direction, restoring the spring force to a constant amount, and this operation is repeated. This operation ensures that the spring force stored in the torsion spring 72 remains at the desired constant amount.

On the other hand, when braking is released, the drive unit 9 is activated by a command from the control device. Specifically, the electric motor 32 rotates in the braking release direction, and this rotation in the braking release direction is transmitted to the spindle 40 via the reduction gear mechanism 33. As a result, as the spindle 40 rotates in the braking release direction, the nut member 41 and piston 18 that are threaded onto the spindle 40 move back toward their initial positions (one end), creating a predetermined clearance between the inner brake pad 2, outer brake pad 3, and the disc rotor D, and releasing the braking force.

When the brake is released, as the spindle 40 rotates in the brake release direction, the tip 92 of the spring clutch 73 abuts against the other opposing wall surface 90B (see Figure 7) that faces circumferentially along the engagement slit portion 90 of the torque transmission member 71, reducing the clamping force of the spring clutch 73 on the spindle 40. As a result, the rotation of the spindle 40 in the brake release direction is not transmitted to the torque transmission member 71 via the spring clutch 73, but the restoring force of the torsion spring 72, which was elastically deformed during braking, causes the torque transmission member 71 to rotate in the brake release direction and return to its initial position.

Furthermore, if a power source or other failure occurs during braking and the electric motor 32 does not generate rotational torque, the fail-open mechanism 35 of the drive unit 9 is activated. That is, if the electric motor 32 does not operate normally during braking, the torsion spring 72, which was elastically deformed during braking, returns to its original position, i.e., the elastic energy stored during braking is released. The torque transmission member 71 then rotates in the brake release direction due to the restoring force of the torsion spring 72. Because the clamping force exerted by the spring clutch 73 toward the radial center of the spindle 40 is large, the spindle 40 rotates in the brake release direction and returns to near its initial position as the torque transmission member 71 rotates in the brake release direction (returning to its initial position). As a result, the nut member 41 and piston 18 retract toward their initial positions, reducing the braking force exerted on the disc rotor D by the pair of inner and outer brake pads 2, 3. The vehicle can then be moved to a safe location and stopped.

As described above, in the disc brake 1A according to the first embodiment, the torque transmission member 71 is positioned radially outward of the spindle 40, and the spring clutch 73 is provided between the cylindrical support portion 46 of the spindle 40 and the small-diameter cylindrical portion 84 of the torque transmission member 71. As a result, in the disc brake 1A according to the first embodiment, the axial length of the disc rotor D can be shortened. This improves the layout flexibility of the disc brake 1A according to the first embodiment, making it easier to mount on a vehicle.

In addition, the disc brake 1A according to the first embodiment employs a spring clutch 73 as a torque limiter mechanism that rotates the torque transmission member 71 together with the spindle 40 until the rotational resistance with the spindle 40 exceeds a predetermined amount of elastic deformation (predetermined spring force) in the torsional direction of the torsion spring 72. As a result, a substantially constant amount of spring force, neither excessive nor insufficient, can be accumulated in the torsion spring 72 during braking.

Furthermore, by employing the spring clutch 73 as the torque limiter mechanism, rotation of the spindle 40 in the brake release direction is not transmitted to the torque transmission member 71 via the spring clutch 73, particularly when the brake is released during normal driving. Instead, the torque transmission member 71 rotates in the brake release direction due to the restoring force of the torsion spring 72, preventing the torque transmission member 71 from rotating past its initial position in the brake release direction. This ensures more stable operation of the fail-open mechanism 35. As a result, there is no need to provide a means for restricting relative rotation of the torque transmission member 71 with respect to the fixed member 70 (described in detail later), simplifying the structure and ultimately achieving a more compact design.

Furthermore, in the disc brake 1A according to the first embodiment, the spring clutch 73 and the torsion spring 72 are arranged so as to overlap each other when viewed from the radial direction. Also, the spindle 40 and the torsion spring 72 are arranged so as to overlap each other when viewed from the radial direction. This allows the axial length of the disc rotor D in the disc brake 1A to be further shortened.

Furthermore, in the disc brake 1A according to the first embodiment, the coil portion 93 of the spring clutch 73 is wound around the annular groove portion 48 of the spindle 40 with a tightening force when assembled. As a result, the responsiveness (quick rotation) of the torque transmission member 71 to the rotation of the spindle 40 during braking can be improved. This also improves the responsiveness to the accumulation of elastic energy in the torsion spring 72 as the spindle 40 rotates, thereby ensuring stable operation of the fail-open mechanism 35.

Next, a disc brake 1B according to a second embodiment will be described based on Figures 9 and 10, and also with reference to Figure 1 as appropriate. When describing the disc brake 1B according to the second embodiment, only the differences from the disc brake 1A according to the first embodiment will be described.
Referring particularly to Figure 9 , the disc brake 1B according to the second embodiment employs a truncated conical spring 100 instead of the spring clutch 73 employed in the disc brake 1A according to the first embodiment. More specifically, referring to Figure 10 , an inner flange portion 102 is formed near one end of the small-diameter cylindrical portion 84 of the torque transmission member 71, protruding radially inward. The inner flange portion 102 is formed in an annular shape. The inner diameter of the inner flange portion 102 is larger than the outer diameter of the male thread portion 44 of the spindle 40 and smaller than the outer diameter of the cylindrical support portion 46 of the spindle 40. One end face of the inner flange portion 102 and the other end face of the cylindrical support portion 46 of the spindle 40 are disposed adjacent to each other in the axial direction.

A truncated conical spring 100 is disposed between the inner flange portion 102 of the torque transmission member 71 and the annular support portion 45 of the spindle 40. The truncated conical spring 100 is cylindrical with a predetermined thickness and has an outer shape formed in a truncated cone. The truncated conical spring 100 elastically deforms and expands/contracts due to a compressive load applied along the axial direction. The cylindrical support portion 46 of the spindle 40 is disposed within the truncated conical spring 100. The large-diameter side of the truncated conical spring 100 is disposed at the boundary between the inner surface of the small-diameter cylindrical portion 84 of the torque transmission member 71 and the inner flange portion 102. Meanwhile, the small-diameter side of the truncated conical spring 100 is disposed at the boundary between the annular support portion 45 of the spindle 40 and the cylindrical support portion 46.

In the disc brake 1B according to the second embodiment, the truncated conical spring 100 corresponds to the elastic body that acts as a torque limiter mechanism. The annular support portion 45 of the spindle 40 corresponds to the outer peripheral flange portion. Referring to FIG. 10, in the disc brake 1B according to the second embodiment, as in the disc brake 1A according to the first embodiment, a retaining ring 98 is formed between a notched step portion 60 provided at one end of the annular support portion 45 of the spindle 40 and an annular groove portion 95 provided on the inner surface of the large-diameter cylindrical portion 85 of the torque transmission member 71. As a result, axial movement of the spindle 40 relative to the torque transmission member 71 is restricted.

Referring to FIG. 10 , the truncated conical spring 100 is installed between the inner flange portion 102 of the torque transmission member 71 and the annular support portion 45 of the spindle 40 with a slight compressive load applied during assembly. In other words, the truncated conical spring 100 is installed during assembly in a state in which it applies a biasing force in a direction that separates the inner flange portion 102 of the torque transmission member 71 and the annular support portion 45 of the spindle 40 (see the white arrow in FIG. 10 ). When the spindle 40 rotates in the braking direction, the rotation of the spindle 40 is transmitted to the torque transmission member 71 via the truncated conical spring 100 until the rotational resistance force between the truncated conical spring 100 and the spindle 40 and torque transmission member 71 exceeds a predetermined amount of elastic deformation (predetermined spring force) in the torsional direction of the torsion spring 72. The spindle 40, the truncated conical spring 100, and the torque transmission member 71 are arranged to overlap each other when viewed in the radial direction.

In the disc brake 1B according to the second embodiment, when the spindle 40 rotates in the braking direction during braking during normal driving, the torque transmission member 71 rotates in the braking direction together with the truncated conical spring 100 in conjunction with the rotation of the spindle 40 due to the rotational resistance force generated between the truncated conical spring 100 and the spindle 40 and torque transmission member 71. As the torque transmission member 71 rotates in the braking direction relative to the fixed member 70, which is supported non-rotatably, the torsion spring 72, which is disposed between the torque transmission member 71 and the fixed member 70, is elastically deformed in the torsional direction, storing elastic energy.

As the spindle 40 continues to rotate in the braking direction and the torsion spring 72 reaches a predetermined amount of elastic deformation in the torsional direction, the spring force exceeds the rotational resistance force generated between the truncated conical spring 100 and the spindle 40 and torque transmission member 71, causing slippage between the truncated conical spring 100 and the spindle 40 and torque transmission member 71. As a result, the torque transmission member 71 does not rotate in the braking direction, and the spring force accumulated in the torsion spring 72 is limited to a fixed amount.

On the other hand, when the spindle 40 rotates in the brake release direction, the torque transmission member 71 rotates in the brake release direction together with the truncated conical spring 100 due to the rotational resistance force generated between the truncated conical spring 100, the spindle 40, and the torque transmission member 71, as well as the restoring force of the torsion spring 72. In other words, the restoring force of the torsion spring 72 acts as a rotational torque in the brake release direction and is applied to the spindle 40 rotating in the brake release direction via the torque transmission member 71 and the truncated conical spring 100. As the spindle 40 rotates in the brake release direction, the nut member 41 and piston 18 move back toward their initial positions (toward one end), creating a predetermined clearance between the inner brake pad 2, outer brake pad 3, and the disc rotor D, thereby releasing the braking force.

Furthermore, if a power source or other failure occurs during braking and the electric motor 32 does not operate normally, the torsion spring 72, which was elastically deformed during braking, returns to its original position, i.e., the elastic energy stored during braking is released. The restoring force of the torsion spring 72 then causes the torque transmission member 71 to rotate in the brake release direction. Because the rotational resistance generated between the truncated cone spring 100 and the spindle 40 and torque transmission member 71 is large, the rotation of the torque transmission member 71 in the brake release direction (returns to its initial position) causes the spindle 40 to rotate in the brake release direction and return to near its initial position. As a result, the nut member 41 and piston 18 move back toward their initial positions, reducing the braking force exerted on the disc rotor D by the pair of inner and outer brake pads 2, 3.

In the disc brake 1B according to the second embodiment described above, similar to the disc brake 1A according to the first embodiment, the torque transmission member 71 is positioned radially outward of the spindle 40, and a truncated conical spring 100 is provided between the annular support portion 45 of the spindle 40 and the inner flange portion 102 of the torque transmission member 71. This allows the axial length of the disc rotor D in the disc brake 1B to be shortened. Furthermore, in the disc brake 1B according to the second embodiment, the torsion spring 72 can be charged with just the right amount of spring force during braking, ensuring more stable operation of the fail-open mechanism 35.

Furthermore, in the disc brake 1B according to the second embodiment, the truncated conical spring 100 and the torsion spring 72 are arranged so as to overlap each other when viewed radially. This allows the length of the disc brake 1B along the axial direction of the disc rotor D to be further shortened.

Furthermore, in the disc brake 1B according to the second embodiment, the truncated conical spring 100 is installed in a state in which, during assembly, it applies a biasing force in a direction that separates the inner flange portion 102 of the torque transmission member 71 and the annular support portion 45 of the spindle 40 from each other. As a result, the responsiveness (quick rotation) of the torque transmission member 71 to the rotation of the spindle 40 during braking can be improved. This also improves the responsiveness to the accumulation of elastic energy in the torsion spring 72 as the spindle 40 rotates, thereby ensuring stable operation of the fail-open mechanism 35.

In the disc brake 1B according to the second embodiment described above, a relative rotation restricting means may be provided between the torque transmission member 71 and the fixed member 70. The relative rotation restricting means restricts the initial relative position of the torque transmission member 71 and the fixed member 70 along the circumferential direction during assembly, and a limit relative position that restricts the amount of relative rotation of the torque transmission member 71 when the torque transmission member 71 rotates relative to the fixed member 70. In this embodiment, a set load can be applied to the torsion spring 72 during assembly, thereby increasing the return force of the torsion spring 72. As a result, even if the electric motor 32 cannot operate due to a power supply failure or the like during braking, the return force of the torsion spring 72 can more reliably release the braking force applied to the disc rotor D by the pair of inner and outer brake pads 2, 3.

In addition, in this embodiment, the above-mentioned relative rotation restriction means is provided, and a set load can be applied to the torsion spring 72 during assembly, thereby improving the responsiveness (quick elastic deformation) of the torsion spring 72 to the rotation of the torque transmission member 71 during braking. In other words, even a slight rotation of the torque transmission member 71 can cause the torsion spring 72 to elastically deform and store elastic energy, improving the responsiveness of the torsion spring 72 to the rotation of the torque transmission member 71.

In addition, since this embodiment is provided with the above-mentioned relative rotation restriction means, the torsion spring 72 does not exceed its initial torsion angle and return to the brake release direction, such as when braking is released during normal driving. In other words, when braking is released during normal driving, the rotational resistance generated between the truncated conical spring 100 and the torque transmission member 71 and spindle 40 causes the torque transmission member 71 to rotate beyond its initial position in the brake release direction as the spindle 40 rotates in the brake release direction. This prevents the torsion spring 72 from twisting in the reverse direction beyond its free state, thereby preventing the coil portion from expanding, ensuring more stable operation. This relative rotation restriction means is effective for the fail-open mechanism 35 employed in the disc brake 1B according to the second embodiment.

Next, a disc brake 1C according to a third embodiment will be described based on Figure 11, with reference also to Figure 1 as appropriate. When describing the disc brake 1C according to the third embodiment, only the differences from the disc brake 1A according to the first embodiment will be described. Note that in Figure 11, only one side of the cylinder portion 13, torque transmission member 114, spring clutch 73, torsion spring 72, and thrust bearing 50 is shown relative to the radial center axis.

In the disc brake 1C according to the third embodiment, a nut member 105 serving as the rotary-linear motion conversion mechanism 34 is connected to the output member of the reduction gear mechanism 33 so as not to rotate relative to the output member. As a result, rotational torque is transmitted between the output member of the reduction gear mechanism 33 and the nut member 105. A push rod 106 is threadedly engaged with the nut member 105. The push rod 106 is supported within the cylinder portion 13 so as not to rotate relative to the output member but so as to be movable along the axial direction. A push plate 108 for pressing the inner brake pad 2 is connected to the other end of the push rod 106. As the nut member 105 rotates, the push rod 106 moves along the axial direction. In the disc brake 1C according to the third embodiment, the nut member 105 corresponds to the rotating member, and the push rod 106 corresponds to the linear motion member.

An annular flange portion 111 protrudes radially outward from the other end of the nut member 105. A thrust bearing 50 is disposed between one end face of the annular flange portion 111 and the cylinder portion 13. A torque transmission member 114 of the fail-open mechanism 35 is disposed radially outward from the annular flange portion 111 of the nut member 105. The torque transmission member 114 is formed cylindrically as a whole. The torque transmission member 114 includes a cylindrical portion 117 and an annular flange portion 118 extending radially inward from the other end of the cylindrical portion 117. The torque transmission member 114 and the cylinder portion 13 are connected by a torsion spring 72. A spring clutch 73 is disposed between the inner circumferential surface of the annular flange portion 118 of the torque transmission member 114 and the outer circumferential surface of the annular flange portion 111 of the nut member 105.

In the disc brake 1C according to the third embodiment, the push rod 106, nut member 105, spring clutch 73, and torque transmission member 114 are arranged to overlap when viewed from the radial direction. Also, the push rod 106, nut member 105, torque transmission member 114, and torsion spring 72 are arranged to overlap when viewed from the radial direction. In the disc brake 1C according to the third embodiment, the cylinder portion 13 corresponds to the fixed portion.

In the disc brake 1C according to the third embodiment, when braking during normal driving, the electric motor 32 is driven by a command from the control device, and rotation in the braking direction is transmitted to the nut member 105 via the reduction gear mechanism 33. Next, when the nut member 105 rotates in conjunction with the rotation of the reduction gear mechanism 33, the push rod 106 threadedly engaged with the nut member 105 advances, advancing the inner brake pad 2 via the push plate 108. As the push plate 108 advances, the inner brake pad 2 and the outer brake pad are clamped against the disc rotor D, generating a braking force.

When the nut member 105 rotates in the braking direction during this braking, the tightening force (rotational resistance force between the nut member 105 and the spring clutch 73) applied by the spring clutch 73 toward the radial center of the nut member 105 gradually increases, causing the torque transmission member 114 to rotate in the braking direction together with the spring clutch 73 as the nut member 105 rotates. Then, as the torque transmission member 114 rotates relative to the cylinder portion 13 in the braking direction, the torsion spring 72 disposed between the torque transmission member 114 and the cylinder portion 13 elastically deforms in the torsional direction, storing elastic energy.

On the other hand, when braking is released, the electric motor 32 rotates in the brake release direction in response to a command from the control device, and this rotation in the brake release direction is transmitted to the nut member 105 via the reduction gear mechanism 33. As a result, as the nut member 105 rotates in the brake release direction, the push rod 106 and push plate 108 that are threadedly engaged with the nut member 105 move back toward their initial positions, creating a predetermined clearance between the inner brake pad 2 and outer brake pad 3 and the disc rotor D, and releasing the braking force.

When the nut member 105 rotates in the brake release direction during this brake release, the tightening force of the spring clutch 73 on the nut member 105 decreases. As a result, the rotation of the nut member 105 in the brake release direction is not transmitted to the torque transmission member 114 via the spring clutch 73, but the restoring force of the torsion spring 72, which was elastically deformed during braking, causes the torque transmission member 114 to rotate in the brake release direction and return to its initial position.

Furthermore, if a power source or other failure occurs during braking and the electric motor 32 does not operate normally, the torsion spring 72, which was elastically deformed during braking, returns to its original position, i.e., the elastic energy stored during braking is released. The torque transmission member 114 then rotates in the brake release direction due to the restoring force of the torsion spring 72. Because the tightening force of the spring clutch 73 toward the radial center of the nut member 105 is large, the rotation of the torque transmission member 114 in the brake release direction (returning to its initial position) causes the nut member 105 to rotate in the brake release direction and return to near its initial position. As a result, the push rod 106 and push plate 108 move back toward their initial positions, reducing the braking force exerted on the disc rotor D by the pair of inner and outer brake pads 2, 3.

In the disc brake 1C of the third embodiment described above, the push rod 106, nut member 105, spring clutch 73, and torque transmission member 114 are particularly arranged to overlap when viewed radially. As a result, the axial length of the disc rotor D can also be shortened in the disc brake 1C of the third embodiment. This improves layout flexibility and makes the disc brake 1C of the third embodiment easier to mount on a vehicle.

The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

This application claims priority to Japanese Patent Application No. 2021-206048, filed December 20, 2021. The entire disclosure of Japanese Patent Application No. 2021-206048, filed December 20, 2021, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

1A, 1B, 1C Disc brake (electric brake device), 2 Inner brake pad (friction pad), 3 Outer brake pad (friction pad), 9 Drive unit, 13 Cylinder portion (fixed portion), 32 Electric motor, 34 Rotation-to-linear motion conversion mechanism, 35 Fail-open mechanism, 40 Spindle (rotating member), 41 Nut member (linear motion member), 45 Annular support portion (outer peripheral flange portion), 48 Annular groove portion, 70 Fixed member (fixed portion), 71 Torque transmission member, 72 Torsion spring (elastic member), 73 Spring clutch (torque limiter mechanism), 90 Engagement slit portion (fitting portion), 100 Truncated conical spring (elastic body, torque limiter mechanism), 102 Inner peripheral flange portion, 105 Nut member (rotating member), 106 Push rod (linear motion member), 114 Torque transmission member, D Disc rotor (disc)

Claims (14)

An electric brake device, the electric brake device comprising:
An electric motor;
a rotating member that is rotated by the driving of the electric motor;
a linear motion member that moves linearly in the axial direction of the disk as the rotating member rotates, thereby moving the friction pad;
a torque transmission member;
a torque limiter mechanism that is disposed between the rotating member and the torque transmission member, and that applies a rotational resistance force between the rotating member and the torque limiter mechanism as the rotating member rotates, and causes the torque transmission member to rotate together with the rotating member until the rotational resistance force exceeds a predetermined value;
A fixed portion;
an elastic member having one end connected to the torque transmission member and the other end connected to the fixed part, and in which elastic energy is stored when the torque transmission member rotates relative to the fixed part as the rotating member rotates;
An electric brake device comprising: 2. The electric brake device according to claim 1,
The elastic member is
The elastic energy is stored when the electric motor rotates forward to move the friction pad in a direction pressing the friction pad against the disk,
An electric brake device in which the elastic energy is released during reverse travel when the electric motor rotates in a reverse direction to move the friction pad in a direction away from the disc, thereby applying a reverse torque to the rotating member. 3. The electric brake device according to claim 1,
The electric brake device, wherein the elastic member is a torsion spring. 2. The electric brake device according to claim 1 ,
The electric brake device, wherein the torque limiter mechanism and the elastic member are arranged to overlap each other when viewed in a radial direction of the rotating member. 5. The electric brake device according to claim 4,
An electric brake device, wherein the elastic member and the linearly acting member are arranged to overlap each other when viewed in a radial direction of the rotating member. 2. The electric brake device according to claim 1 ,
the torque limiter mechanism is a spring clutch wound around an annular groove provided on an outer periphery of the rotating member,
One end of the spring clutch is fitted into a fitting portion provided on the torque transmission member. 7. The electric brake device according to claim 6,
The spring clutch is wound around the annular groove portion with a tightening force when assembled to the electric brake device. 2. The electric brake device according to claim 1 ,
an inner flange portion protruding from the inner circumferential surface of the torque transmission member toward the radially inward direction of the torque transmission member, and an outer flange portion protruding from the outer circumferential surface of the rotating member toward the radially outward direction of the rotating member. 9. The electric brake device according to claim 8,
The electric brake device, wherein the elastic body is installed in a state where, when assembled, it applies a biasing force in a direction that separates the inner peripheral flange portion and the outer peripheral flange portion from each other. 2. The electric brake device according to claim 1 ,
The electric brake device, wherein the elastic member is installed in a state in which a set load is applied when assembled. 2. The electric brake device according to claim 1 ,
the rotating member is a spindle;
The linear motion member is a nut member that is threadedly engaged with the spindle. 2. The electric brake device according to claim 1 ,
the rotating member is a nut member,
The linearly acting member is a push rod that is threadedly engaged with the nut member. An electric brake device, the electric brake device comprising:
An electric motor;
a rotating member connected to the electric motor;
a linear motion member screwed with the rotary member;
a torque transmission member;
a torque limiter mechanism that is disposed between the rotating member and the torque transmission member, and that applies a rotational resistance force between the rotating member and the torque limiter mechanism as the rotating member rotates, and causes the torque transmission member to rotate together with the rotating member until the rotational resistance force exceeds a predetermined value;
A fixed portion;
a torsion spring having one end connected to the torque transmission member and the other end connected to the fixed portion;
An electric brake device comprising: A drive unit that provides power to press friction pads against a disc of a disc brake,
An electric motor;
a rotating member that is rotated by the driving of the electric motor;
a linearly moving member that moves linearly as the rotating member rotates;
a torque transmission member;
a torque limiter mechanism that is disposed between the rotating member and the torque transmission member, and that applies a rotational resistance force between the rotating member and the torque limiter mechanism as the rotating member rotates, and causes the torque transmission member to rotate together with the rotating member until the rotational resistance force exceeds a predetermined value;
A fixed portion;
an elastic member having one end connected to the torque transmission member and the other end connected to the fixed part, and in which elastic energy is stored when the torque transmission member rotates relative to the fixed part as the rotating member rotates;
A drive unit comprising: